Tomato Brown Rot I am told inconsistent water is the cause. What does that...

Asked August 24, 2017, 7:18 PM EDT

Tomato Brown Rot I am told inconsistent water is the cause. What does that mean? Should I keep the soil damp to say 6 inches at all times? If tomatoes show evidence brown now, can I save the crop with calcium fertilizer? Water daily? Please reply

Lane County Oregon irrigation and water management horticulture tomatoes

1 Response

Good afternoon! Is the rot you're describing occurring at the blossom end of the fruit? If so, this is commonly called blossom end rot, and it is the result of a lack of calcium in the fruit. It commonly occurs on the first fruit of the season when plants are still actively growing and calcium is following the flow of water to the leaves. Later in the season, "inconsistent water" can contribute to this problem, as can a lack of calcium in the soil. Applying a calcium chloride spray (which is commonly available in many garden centers) directly to the fruit can help prevent this in fruit that has not yet developed the symptoms. This issue seems to be worse for some varieties than in others. Quali T 23 and Roma are two varieties I have had issues with in the past. If you have never had a soil test, now is a great time to take one, as lime can be added in the fall to prevent this issue next year. Here are a couple of links you may find useful...

https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/ec628.pdf

https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/em8677_0.pdf

Excessive nitrogen can also cause blossom end rot, because it promotes foliar growth that steals the calcium from developing fruit. Regarding irregular water, tomatoes have very deep roots once established (unless in pots, of course), so you don't want to water too often. My general rule of thumb is to let the soil dry out to the touch up to the first knuckle on your index finger, which is a depth of about 1 inch. Watering once or twice a week should be adequate.